The present invention relates to an installation for preliminary crushing of articles, and particularly but not exclusively vehicle wrecks and the like.
In order to recover materials and in particular metals from motor vehicle wrecks or the like, in particular, it is known to make use of crushing installations.
The operation of such a crusher unit is subject to various risks, such as explosions, fire, machinery being broken, etc. These incidents are mainly caused by inserting into the crusher, in amongst the wrecks, hollow bodies such as tanks, gas cylinders, vessels containing liquid petroleum gas (LPG), or solid pieces.
For transporting car wrecks to be profitable, recycling professionals need to begin by compressing the wrecks. The packets obtained in this way present various drawbacks in terms of processing performed by crushing. Firstly, given their density and hardness, the packets are difficult for a crusher to absorb. Secondly, such packets may contain hollow bodies which run the risk of leading to explosions during crushing. The risk of explosion is also present when processing car wrecks that have not been compressed, for example fuel may be present in the tanks.
To solve that problem, proposals have been made to use preliminary crushers which are intended to prepare wrecks whether compressed or non-compressed, prior to crushing proper, by subjecting them to preliminary shredding. This operation considerably increases the productivity of crushers and it eliminates the risk of explosions.
Preliminary crushers operate on the basis of passing materials for pre-shredding between two shafts carrying shredding teeth and turning at different speeds.
Accompanying FIG. 1 is a diagram of such a preliminary crusher of known type.
Within an enclosure 10, there are two mutually parallel horizontal shafts 12 and 14 provided on their peripheries with shredding teeth such as 16. A bottom shaft 14 serves essentially to drive the articles or substances that are to be prepared for crushing, and a top shaft 12 co-operates in rotation with the shaft 14 and actually performs preliminary crushing, given that the two arms rotate in opposite directions and have different speeds of rotation.
The shafts 12 and 14 can be rotated by means of a single motor driving one of the shafts directly, with a gearing system then serving to drive the other shaft.
An improvement to that drive, as disclosed in patent application WO 98/07519, consists in using two drive motors each associated with a respective one of the shafts 12 and 14, said motors being controlled independently as a function of various operating conditions of the installation.
That improves the efficiency of the installation since continuous monitoring over certain operating parameters makes it possible to adapt better to external conditions: the nature of the fill, the speed of filling, etc.
Nevertheless, that type of installation presents problems associated with very frequent xe2x80x9ccobblesxe2x80x9d due to massive bodies being introduced into the preliminary crusher of a kind liable to break the teeth 16, the shafts, or other parts of the installation. In addition, cobbles can cause an entire installation to be stopped; in any event, once too many of the teeth 16 have been destroyed or damaged, the corresponding shaft needs to be replaced, and that is harmful in terms of efficiency and thus of cost.
On that type of known installation, it has also been observed that when an article is introduced that is massive, not deformable, and/or of a size that is greater than the spacing between the two shafts 12 and 14, the system becomes jammed suddenly giving rise, in a fraction of a second, to an infinite surge of torque on the shafts.
Faced with that problem, the present invention proposes a technical solution making it possible both to reduce the inertia and to absorb the energy created by the shafts 12 and 14 being jammed suddenly and violently.
Thus, the present invention provides an installation for preliminary crushing of articles, the installation comprising at least a first shaft for driving articles and a second shaft for shredding driven articles, each of said shafts being provided with shredding teeth and each being rotated by at least one motor, a gearbox for reducing the speed of each motor being placed between each motor and the associated shaft, the installation further comprising both means for controlling said motors in association with sensors for picking up operating parameters of the installation, and data acquisition and processor means.
According to a characteristic of the invention, the installation further comprises a universal joint disposed between the outlet shaft of each motor and the inlet shaft of each gearbox, and each gearbox is mounted to stand on shock absorber means, thus enabling the energy created by impacts and/or torques above a given threshold at the teeth to be absorbed.
This feature of the invention creates elasticity between certain elements of the installation such that impacts or other incidents on the teeth do not necessarily cause all or part of the installation to be destroyed as is the case in known installations.
Surprisingly, although the installation is of considerable size and weight, a degree of flexibility is nevertheless obtained between some of its component parts.
Advantageously, the shock absorber means comprise a shock absorbing element such as a stack of Belleville washers or a hydraulic actuator.
In addition, the installation of the invention may include a safety sensor placed on each shock absorber means and connected to the data processor means which responds by stopping at least the drive motors whenever said sensors are actuated.
A safety sensor responds, in fact, to the shock absorber means being subjected to a large amount of displacement, where such displacement is due to large torque being applied to the shafts, i.e. to an incident.
Thus, the stopping of the motors due to an accidental jamming of the teeth constitutes a safety factor which is entirely necessary for proper operation of the installation.
Advantageously, at least one force sensor is located on the shock absorber means and is connected to the data acquisition and processor means.
The force sensor thus provides continuous information about the forces exerted on each shaft. This information can also be processed by the data acquisition and processor means. For example, values can be displayed in real time on a monitor screen using graphics (in particular for the slow shaft and for the fast shaft) and all of the data can be transcribed by means of a printer.
In accordance with the invention, the installation further comprises decoupler means for separating at least one of the shafts from the associated drive motor.
This is to reduce inertia between at least one of the shafts and the associated motor, in particular in the event of a violent impact between the two shafts. The decoupler means thus perform a function of protecting the drive motors against torque surges, e.g. created by a violent impact.
More precisely, the decoupler means comprise at least one torque limiter.
If only one torque limiter is to be included in the installation, then it is preferably mounted on the second shaft (the shredding shaft) so as to protect the transmission system that operates at the higher speed of rotation and on which the torque created by a jam is greater.
Nevertheless, it is entirely possible and indeed advantageous to fit a torque limiter on each shaft system.
The torque limiter(s) thus provide a mechanical type of protection function for one or both motors in the event of a torque surge on the shafts.
Various types of sensor can be mounted in the installation of the invention.
It is possible to dispose a speed sensor on at least one of the motors (the drive motor and/or the shredding motor), said sensor being connected to the data acquisition and processor means.
In addition, a tripping detector may be provided on the decoupler means in order to monitor said tripping of the decoupler.
Naturally, these various sensors are connected to the data acquisition and processor means which, as explained below, serve not only to provide continuous monitoring and efficient and optimized control over the installation, but also present the advantage of reducing reaction time in the event of a violent impact.
This aspect relating to the safety of the installation represents an improvement that is particularly advantageous and appreciated by users.
The motors driving the shafts are preferably electric motors, i.e. DC or AC motors.
The type of motor should be selected as a function of the power it is to deliver and/or as a function of its size.